<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <div id="app">
        <p>总数：{{ total }}</p>
        <my-component
            @increase="handleGetTotal"
            @reduce="handleGetTotal"></my-component>
    </div>
    <script src="https://unpkg.com/vue/dist/vue.min.js"></script> 
    <script>
        Vue.component('my-component',{
            template:'\
            <div>\
            <button @click="handleIncrease">+1</button>\
            <button @click="handleReduce">-1</button>\
            <div>',
            data:function () {
                return {
                    counter: 0
                }
            },
            methods: {
                handleIncrease:function () {
                    this.counter++; 
                    this.$emit('increase',this.counter);
                },
                handleReduce:function () {
                    this.counter--;
                    this.$emit('reduce', this.counter);
                },
                handleReduce:function () {
                    this.counter--;
                    this.$emit('reduce', this.counter);
                }
            }
        });

        var app = new Vue({
            el:"#app",
            data:{
                total:0
            },
            methods: {
                handleGetTotal: function (total) {
                    this.total = total;
                }
            }
        })
    </script>
</body>
</html>
